Up until 1965, all United States dimes, quarter dollars and half dollars were made of 90% silver and 10% copper. The Coinage Act of 1965 changed the compositions of these coins to reduce or eliminate their silver content because the price of silver had risen above the face value of the coins.

Dimes and quarters were replaced with clad coinage that was a 75% copper/25% nickel outer layer bonded to an inner core of pure copper.

The 90% silver content of the 1964 Kennedy Half Dollar was reduced between 1965 and 1970 to a net composition of 40% silver with outer layers of 80% silver/20% copper bonded to an inner core of .209 silver and .791 copper.

The silver content was completely eliminated in 1971 when half dollars and dollars met the same fate the dimes and quarters had in 1965.

A collectible silver coin was made from 1971 to 1976 however. Eisenhower Dollars containing a net composition of 40% silver were made especially for collectors. Coins released for circulation during this time were of the copper/nickel clad variety.